2021 Mercedes-Benz Amg Cla 45 S 4Matic+ — MOT failures & pass rate
Across 464 MOT tests, the 2021 Mercedes-Benz Amg Cla 45 S 4Matic+ recorded an 87.5% pass rate. That is 3.9 percentage points worse than all cars of a similar age, which fail at 8.6%. Failures cluster in tyres, lighting & signalling and emissions & environmental.
What the MOT record shows
One area stands out: tyres, recorded in 9.3% of tests against 1.7% for the next-worst category.
At component level the recurring items are headlamp aim, registration plates and catalyst emissions — headlamp aim alone was recorded 12 times.
Tyres is the most common advisory, noted on 14.7% of tests — work that passed today but is likely due soon.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 9.3% | 43 |
| 2 | Lighting & signalling | 1.7% | 8 |
| 3 | Emissions & environmental | 1.1% | 5 |
| 4 | Brakes | 0.9% | 4 |
| 5 | Visibility | 0.7% | 3 |
| 6 | Other defects | 0.7% | 3 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 12 |
| 2 | Registration plates | 5 |
| 3 | Catalyst emissions | 5 |
| 4 | Tread depth | 4 |
| 5 | Brake pads | 2 |
| 6 | Washers | 2 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 14.7% | 68 |
| 2 | Brakes | 6.0% | 28 |
| 3 | Other defects | 4.1% | 19 |
| 4 | Visibility | 2.8% | 13 |
| 5 | Suspension | 0.9% | 4 |
| 6 | Body, structure & corrosion | 0.2% | 1 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 283 | 12.0% |
| 30-60k | 159 | 11.9% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2024 | 219 | 10.5% |
| 2025 | 235 | 14.5% |
What to check before buying a 2021 Amg Cla 45 S 4Matic+
The failure pattern for this year is specific enough to inspect against: tyres accounted for 9.3% of tests. Start there.
- Tyres (9.3% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (1.7% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (1.1% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2021 Mercedes-Benz Amg Cla 45 S 4Matic+s pass their MOT?
87.5% of the 464 2021 Mercedes-Benz Amg Cla 45 S 4Matic+ MOT tests in this dataset passed — a 12.5% fail rate.
What is the most common MOT failure on a 2021 Mercedes-Benz Amg Cla 45 S 4Matic+?
Tyres, recorded in 9.3% of tests, followed by lighting & signalling (1.7%).
Does the 2021 Amg Cla 45 S 4Matic+ get worse with mileage?
Its MOT fail rate rises from 12.0% in the 0-30k band to 11.9% in the 30-60k band.
Methodology & source. Based on 464 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.